I got a standard early one Terry but not used it with a phone camera. It does light up the fly nicely and not too harsh a light.
Beware if you do opt for one, you'll get stung for import duties. Anything over £18. from Russia.
I bought one. Only used it once. Nowhere near enough light for my dSLR set-up. Ended up with exposures of about 30 seconds! No idea if it is specifically intended for use with smart phones, but not intended for use with dSLRs. PM me if you are interested in buying it off me. Will depend on me being able to find all the bits, as I may have cannibalised some of it...
If you go to B & M stores they have similar ones for "On line streaming" (whatever that is) for between £10 - £25 even comes with an adjustable height stand. Specifically for use with phones. No "Fly adaptor" though.
I have one of the early Russian ones and the B & M ones beat it hands down. I can always adapt a fly stand or put a shelf on it. (I bought a B & M one for the Wife for use with a DSLR, She likes it). I paid £10 for it - No import duties, no waiting ?